The role of the cellular microenvironment in transplant-mediated repair has only recently been examined. We have previously used anatomical and physiological indices of repair to explore the potential role of microvascular development and tissue oxygenation in this dynamic process. Our previous data have shown a stage specific appearance of a low oxygen microenvironment in fetal grafts as early as 1 week post-transplantation with an extension of this embryonic microenvironment into surrounding host tissue. In another set of experiments, we have found that transplantation of fetal cells into a well-characterized model of spinal cord injury evokes behavioral modifications in this same time period (see preliminary data and appendix). In this proposal, we wish to establish if the development of microvascular elements and other indices of graft function (blood flow, cytochrome oxidase histochemistry and 2- deoxyglucose autoradiography) can be associated with the modification of motor behaviors during the recovery process. Specifically, a combination of anatomical and behavioral/functional analyses will be used to examine the effects of suspension transplants of fetal (14 day) spinal cells after contusion lesions at early (1 day), sub-chronic (10 day), and chronic (28 days) times. Thereafter a combination of techniques will explore: (1) the longitudinal development of conditioned quadrupedal locomotion (gain analysis) for up to 6 months post-injury, (2) the alterations in involuntary motor responses (acoustic startle) that may otherwise be masked by sequelae to spinal injury, (3) the quantitative development of microvascular elements that seem to be one factor in successful graft integration and behavioral expression, (4) how factors that increase the extent of microvascular development and graft size (oral nimodipine administration) concomitantly modify these behaviors, and (5) if physiological indices (blood flow, cytochrome oxidase histochemistry, 2-deoxyglucose autoradiography) of graft differentiation are associated with the anatomical and behavioral changes following neural tissue transplantation. By examining the role of such changes in graft-mediated repair, we can continue the definition of the functional conditions under which transplants will prosper. Furthermore, we can directly test the hypothesis that microvascular dynamics and oxygen transport are associated with successful graft development and the alteration of spontaneous or conditioned behavioral paradigms. The aims and hypothetical construct of this proposal are directly related to those of Projects 1, 4, and 5.